Collapsible steering column assembly

ABSTRACT

A collapsible steering column of the type used on motor vehicles is arranged to telescope upon impact. The steering column is provided with inner and outer telescoping polygonally shaped shafts axially slidable one within the other. The inner and outer shafts are held in rotational and axial driving engagement by clamping means which preloads the respective shafts to withstand normal axial impact but which permits the shafts to collapse axially when the force of impact of a collision exceeds a predetermined safe value.

United States Patent Baker June 26, 1973 COLLAPSIBLE STEERING COLUMNASSEMBLY [75] Inventor: Donald J. Baker, South Bend, Ind.

[73] Assignee: The Bendix Corporation, South Bend, Ind.

[22] Filed: Sept. 27, 1971 [211 App]. No.: 184,149

[52] U.S. Cl. 74/492, 24/279 [51] Int. Cl. B62d 1/18 [58] Field ofSearch 74/492, 493; 24/279, 24/243 B [56] References Cited UNITED STATESPATENTS 912,097 2/1909 Erickson 24/279 Dalpiaz 74/279 3,491,614 l/1970Saunders et al. 74/493 Primary Examiner-Milton Kaufman Attorney-Ken C.Decker et al.

57] ABSTRACT A collapsible steering column of the type used on motorvehicles is arranged to telescope upon impact. The steering column isprovided with inner and outer telescoping polygonally shaped shaftsaxially slidable one within the other. The inner and outer shafts areheld in rotational and axial driving engagement by clamping means whichpreloads the respective shafts to withstand normal axial impact butwhich permits the shafts to collapse axially when the force of impact ofa collision exceeds a predetermined safe value.

12 Claims, 7 Drawing Figures PAIENIEDauues I975 I 3.741.032

sum 1 or 2 INVliN'IOR. DONALD J. BAKER ATTORNEY PMENIEUJIINZS 973 SHEEI2 0? 2 FIG.5

FIG.7

FIG. 6

INVENTOR. DONALD J. BAKER A4 816k I ATTORNEY 1 COLLAISIBLE STEERINGCOLUMN ASSEMBLY BACKGROUND OF THE INVENTION Public clamor for greatersafety in the automotive vehicle has forced a retreat from theconventional steering shaft which is so constructed as to not collapseupon vehicle collision. This non-collapsible type of steering shaft wasresponsible for many chest and head injuries to the driver brought aboutby subjecting him to the full force of impact in a collision.

Accordingly, presently constructed steering shafts are of thecollapsible or energy absorbing types which may, for example, take theforms shown in US. Pats. Nos. 3,318,170; 3,434,369; 3,444,753; and3,491,614 assigned to the common assignee for this invention.

The collapsible steering assembly herein disclosed is proposed asoffering advantages over the prior patented devices.

SUMMARY OF THE INVENTION The principal object of the invention is toprovide a. collapsible steering assembly for an automotive'vehicle,including two telescoping polygonal shafts equipped with a preloadingdevice having two corresponding polygonal openings respectively throughwhich said shafts project in frictional engagement.

Another object of the invention is to provide a collapsible steeringshaft assembly having two polygonally shaped shafts which aretelescopically arranged in lastfree torsional relationship.

A further objectof the invention is to provide a collapsible steeringshaft assembly which is simple to manufacture and easy to assemble.

A still further object of the'invention is to provide clamping means atthe junction of two telescoping shafts which furnishes independentpreloading on the respective shafts for controlling both torsional andaxial response between the shafts.

An important object of the invention is to provide a clamping devicewhich comprises two deflectable arms located at the junction of twooverlapping telescoping shafts so that one of the arms is frictionallyattached to one of the shafts .and the. other arm is frictionallyattached to the other shaft.

Another important object of the invention is to provide a collapsibletelescopingsteering shaft assembly with adjustable means forpreselecting the axial loading required to cause the shaft assembly tocollapse.

- The above and other important objects and features of the inventionwill be apparent from the following description of the device taken inconnection with the accompanying drawing, which form a part of thisspecification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows diagrammetically thecollapsible steering shaft assembly of the present invention associatedwith the dirigible wheels of a vehicle;

FIG. 2 is a fragmentary enlarged view partly in longitudinal section ofthe shaft assembly of FIG. 1;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken on the line 4--4 of FIG. 2 showing therelative shaft positions without torsional loading;

FIG. 5 is a sectional view taken on line 5-5 of FIG. 2 showing shaftrelationship upon clockwise rotation of the shaft assembly;

FIG. 6 is a sectional view'taken on the line 6-6 of FIG. 2 showing shaftrelationship upon counterclockwise rotation of the shaft assembly; and

FIG. 7 is a view in perspective of the clamp shown removed from thetelescoping shafts.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, a collapsiblesteering shaft assembly designated by the numeral 10 is shown associatedwith other elements of a vehicle steering system,

including a steering wheel 12, appropriately connected to the upper endof the assembly 10 through a coupling mechanism 14 and a steering gear16 drivably secured to the lower end of the assembly 10 through acoupling 18. The steering gear 16 is operatively connected to dirigiblewheels 20 in a manner well known to those skilled in the art.

The steering shaft assembly 10, in accordance with the principles of thepresent invention, comprises an outer shaft 22 and an inner shaft 24.The outer shaft 22 is generally tubular in construction totelescopically receive the inner shaft 24. End portion 23 of the outershaft 22-is formed with a polygonal bore to slidably accept acorresponding polygonal end 25 of the shaft 24. This telescopic fit ofthepolygonal shaft ends 23 and 25 provides for torsional rotation of theshafts as well as relative. axial displacement between the inner andouter shafts. However, because of the manufacturing difficultiesencountered in holding the .desiredtolerances between the shafts, it isimpractical to maintain the shafts free of back lash. Moreover, thissame problem in manufacturing rendersit equally impractical to controlthe telescoping shaft tolerances to the degreenecessary to establishaccurately a predetermined axial preload which when exceeded willcollapse the shaft assembly 10. The axial preload on the shafts 22 and24 should be controlled within an acceptable range to insure the properfunctioning of the steering shaft assembly.

To provide a lash'free connection between the shaft ends 23 and 25. andalso establish an axial preload therebetween which when overcome willcollapse the shaft assembly 10, clamping means 26 is located at thejunction between the shaft ends 23 and 25 where shaft overlap occurs.The-clamping means 26comprises a clamp member 27 having two parallelaxially aligned arms 28 and 30 formed with polygonal openings 32 and 34therein respectively to matingly receive the polygonal shaft ends 23 and25. The arms 28 and 30 are joined at their upper end portions by acommon support which is divided into two U-shaped sections 36 and 38separated by a space or slot 40. The space 40 allows for relativelateral movement or adjustment between the common support sections 36and 38m thereby regulate the preload on the shafts 22 and 24 as appliedby the arms 28 and 30.

For adjusting the axial preload of the shaft assembly, means isoperatively connected to the common support sections and comprises abolt 42 which extends through the U-shaped sections 36 and 38 so thathead 44 engages a side of the common support section 36 and nut 46engages a side of thecommon support section 38 opposite from the head44. Washers 48 and50 are located respectively between the head 44 andcommon support 36 and between the nut 46 and common support 38, tofacilitate drawing together of the sections 36 and 38 upon tighteningthe nut 46.

The clamping means 26 is held in assembled relationship to the outershaft 22 by means which includes the bolt 42, one side of which abutsthe so support which carries the arm 28 and the other side of whichengages a nib 52 formed in the outer surface of the end 23 of the outershaft 22. The nib 52 is centrally located on the shaft 29 as to registerwith the slot 40 when assem bling the clamp to the shaft. That is, theclamp member 27 is mounted to the end 23 of the shaft 22 by aligning theopening 32 in the arm 28 with the shaft end 23 so that the slot 40registers with the nib and then sliding the clamp along the shaft, tothe right, as viewed in FIG. 2, until the bolt 42 can be passed betweenthe nib 52 and the inner side of the arm 28. This locks the clamp to theend of the shaft 22 for the assembly of the inner shaft 24.

As shown in FIG. 3, the hexagonal openings 32 and 34 of the arms 28 and30 respectively conform precisely to the geometry of the shaft ends 23and 25 which are in telescopic engagement. This geometric relationshipbetween the sides of the openings 32 and 34 and the respective shaftends 23 and 25 produces the desired gripping action on the shafts by thearms 28 and 30 upon threading the nut 46 on the bolt 42. The arms 28 and30 are preloaded respectively to the shaft ends 23 and 25. That is, thearm 28 is independently preloaded to carry a preselected axial force ofthe shaft 22 and the arm 30 is preloaded to carry the axial force of theshaft 24. When this preloading is exceeded, as might happen in acollision, the shafts telescope, thus absorbing the greater amount ofenergy which otherwise would have been directed into the steering wheel.

In FIG. 4 it will be seen that the sides of the telescoping shaft endsare parallel and concentric during nonsteering conditions, i.e., notorsional loading on the shafts. This shaft relationship is illustratedby the spacing between the sides AB and CD of the shafts. The spacing ortolerance is exaggerated for illustrative purposes. In practicethisspacing would be held to practical manufacturing tolerances. Uponinitial rotation of the shafts, torsional loading is taken through theclamping means 26. The clamp 27 is constructed with some flexibility orspring rate built into it by design which resists torsional stressing upto a given value. When this torsional stress value is exceeded, so as toovercome the energy stored in the clamp, the arms 28 and 30 are causedto deflect laterally. As the torsional stressing or loading on theshafts is increased, lateral deflection of the arms 28 and 30 increases.This torsional loading on the shafts required to estabish engagementbetween the shaft sides'AB and CD for example, depends on such factorsas the dimensions of the clamp 27, alloy of steel, etc. These factorsare, of course, taken into account at the time the design is approved.As seen in FIG. 5, the shafts are subjected to clockwise torsionalstressing or loading in excess of the force built into the clamp so thatthe arms 28 and 30 have been distorted or flexed laterally with respectto each other, thus establishing tated into driving engagement.Obviously, for both directions of shaft, roation, the torsional loadingis now being transferred directly between the shafts 22 and 24.

While this invention has been described in connection with a specificembodiment, it will be understood by those skilled in the an thatchanges may be made in structure and arrangement of parts withoutdeparting from the spirit of the invention. By way of example only andnot limited to the specific illustration, shafts having geometricalshapes other than hexagonal are appropritae in the practice of theinvention.

I claim:

l. A collapsible steering shaft assembly, which comprises:

an outer shaft having an end with a polygonal bore;

an inner shaft having a polygonal end corresponding to said bore andtelescopically received within said bore; said inner and outer shaftshaving axial sliding movement therebetween and torsional backlash; and

means connected to said inner and outer shafts for controlling the axialmovement and torsional backlash of said shafts;

said means including a support and two parallel axially aligned armsintegrally suspeneded from said support, one of said arms is operativelyconnected to one of said shafts and the other of said arms isoperatively connected to the other of said shafts to establish axialpreloading of the respective shafts.

2. A collapsible steering shaft assembly, as defined in claim 1, whereinsaid arms have lateral flexibility with respect to the shaft axes so asto respond to torsional loading.

3. A collapsible steering shaft assembly, as defined in claim 1, whereinsaid telescoping shafts have overlapping ends, and said means forcontrolling the axial movement and torsional backlash of said shafts islocated at the junction of said overlapping ends.

4. A collapsible steering shaft assembly, as'defined in claim 1, whereinsaid means further includes means for adjusting the axial preload ofthe'shafts to a predetermined value so that the assembly will collapsewhen the axial force along the shafts exceeds this value.

5. A collapsible steering shaft assembly, as defined in claim 4, whereinsaid support comprises two U-shaped sections separated by a space andsaid means'for adjusting the axial preload includes a bolt which extendsthrough the U-shaped sections.

6. A collapsible steering shaft assembly, as defined in claim 5, whreinone of said shafts is formed with a nib thereon in registry with thespace between said sections and said bolt engages with nib on one sideand abuts said support on the other side.

7. A collapsible steering shaft assembly, as defined in claim 6, whereinsaid nib is integral with the outer shafts and is located at thejunction of overlap between said telescoping shaft ends.

8. A collapsible steering shaft assembly, as defined in claim 1, whereinsaid two parallel axially aligned arms are in the form of a clamp withpolygonal openings for receiving the respective corresponding polygonalshaft ends.

9. A collapsible steering shaft assembly, as defined in claim 8, whereinsaid polygonal ends of said shafts are formed with flat sides.

10. In a collapsible steering shaft assembly;

an outer shaft and an inner shaft;

one end of said inner shaft having a polygonal cross section;

one end of said outer shaft having a polygonal bore receiving thepolygonal end of said inner shaft; and

clamping means operatively connected to said inner shaft and to saidouter shaft for controlling relative axial movement and torsional.backlash between said shafts;

said clamping means including a'support, a pair of substantiallyparallel arms extending from said support, one of said arms beingoperably connected to said inner shaft, the other arm being operablyconnected to said outer shaft.

11. The invention of claim one of said shafts relative to the othershaft.

4 i l i

1. A collapsible steering shaft assembly, which comprises: an outershaft having an end with a polygonal bore; an inner shaft having apolygonal end corresponding to said bore and telescopically receivedwithin said bore; said inner and outer shafts having axial slidingmovement therebetween and torsional backlash; and means connected tosaid inner and outer shafTs for controlling the axial movement andtorsional backlash of said shafts; said means including a support andtwo parallel axially aligned arms integrally suspeneded from saidsupport, one of said arms is operatively connected to one of said shaftsand the other of said arms is operatively connected to the other of saidshafts to establish axial preloading of the respective shafts.
 2. Acollapsible steering shaft assembly, as defined in claim 1, wherein saidarms have lateral flexibility with respect to the shaft axes so as torespond to torsional loading.
 3. A collapsible steering shaft assembly,as defined in claim 1, wherein said telescoping shafts have overlappingends, and said means for controlling the axial movement and torsionalbacklash of said shafts is located at the junction of said overlappingends.
 4. A collapsible steering shaft assembly, as defined in claim 1,wherein said means further includes means for adjusting the axialpreload of the shafts to a predetermined value so that the assembly willcollapse when the axial force along the shafts exceeds this value.
 5. Acollapsible steering shaft assembly, as defined in claim 4, wherein saidsupport comprises two U-shaped sections separated by a space and saidmeans for adjusting the axial preload includes a bolt which extendsthrough the U-shaped sections.
 6. A collapsible steering shaft assembly,as defined in claim 5, whrein one of said shafts is formed with a nibthereon in registry with the space between said sections and said boltengages with nib on one side and abuts said support on the other side.7. A collapsible steering shaft assembly, as defined in claim 6, whereinsaid nib is integral with the outer shafts and is located at thejunction of overlap between said telescoping shaft ends.
 8. Acollapsible steering shaft assembly, as defined in claim 1, wherein saidtwo parallel axially aligned arms are in the form of a clamp withpolygonal openings for receiving the respective corresponding polygonalshaft ends.
 9. A collapsible steering shaft assembly, as defined inclaim 8, wherein said polygonal ends of said shafts are formed with flatsides.
 10. In a collapsible steering shaft assembly; an outer shaft andan inner shaft; one end of said inner shaft having a polygonal crosssection; one end of said outer shaft having a polygonal bore receivingthe polygonal end of said inner shaft; and clamping means operativelyconnected to said inner shaft and to said outer shaft for controllingrelative axial movement and torsional backlash between said shafts; saidclamping means including a support, a pair of substantially parallelarms extending from said support, one of said arms being operablyconnected to said inner shaft, the other arm being operably connected tosaid outer shaft.
 11. The invention of claim 10: said arms havingopenings therein with polygonal sides for mating engagement respectivelywith their corresponding inner and outer shafts, said openings beingsubstantially coaxial.
 12. The invention of claim 11: said supportmember being divided into two sections separated by a space, said armsbeing connected to each of said sections; a device adjustably connectedbetween the sections of said support to adjust the width of said spaceand therefore the force vented on said shaft by said arms to therebycontrol the force required to move one of said shafts relative to theother shaft.